Zero airline risk is BS. That Patrick Sawyer guy infected the doctor sitting next to him, who subsequently died. If the incubation period can vary from 7 - 21 days they really have no reliable indicator of when he became contagious.
And those he infected infects others and those infect others and so on and so on. The cat is out of the bag and the CDC can't put it back in. No way can they ever think it's possible to round up everyone he came in contact with and who those came in contact with, etc.